Center beam suspension system

ABSTRACT

A vehicle suspension system having a central beam formed with a mounting flange on each side thereof. The beam is pivotally mounted to a suspension frame at one end, and rigidly attached to an axle at another end along substantially the entire length of the axle. A control arm is pivotally mounted to each mounting flange at one end, and to the suspension frame at another end whereby the pivot axis of the center beam and the control arms are axially aligned. Additionally, the pivot connection of the central beam provides one or two bushings which may have a constant spring rate, or which may include a spring rate which varies in the vertical and horizontal direction. In a second and third embodiment, a lift mechanism is provided for raising the axle from a ground engaging to a non-ground engaging position.

This application is a division of application Ser. No. 08/756,947, filedDec. 2, 1996, which application is now: U.S. Pat. No. 5,746,441.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates generally to an improved suspension system forland vehicles. More particularly, the invention relates to trailing beamair suspension systems. Specifically, the invention relates to trailingbeam air suspension systems having a center beam.

2. Background Information

With the advent following World War II of large load carrying capacitytrucks and trailers in this country, came the need to provide vehicleswith multiple axles for increasing the capacity of trucks over that ofpreviously existing designs. While the use of additional axleseffectively increased load-carrying capacity, it was soon realized thatas the number of load bearing axles increased on a given vehicle, anumber of difficulties arose. Specifically, tire scuffing, loss in fueleconomy and the inability to safely corner, all work problems associatedwith multiple axle vehicles. Mitigation of these problems was a primaryconcern to the industry, which concern resulted in the development of avariety of suspension systems, both liftable and non-liftable. Liftablesuspensions could be selectively raised from the road surface or loweredinto engagement with the road surface when needed, thereby mitigating anumber of the aforementioned problems. Additionally, non-liftable axleshave been designed for a variety of purposes, and specifically a numberof specialty chassis-cab type vehicles require additional load-carryingcapacity. More specifically, auxiliary suspension systems are necessaryfor trash compactor trucks and concrete mixing and delivery vehicles.Cab-chassis trucks of this type require additional suspensions as thetruck has a relatively large weight when compared to the overall vehiclelength.

Suspension systems may take a variety of forms, including parallelogramsuspensions, and leading and trailing beam-type suspensions. Generally,leading and trailing beam-type suspensions include a pair oflongitudinally extending beams which may be either flexible or rigid,one of which is located adjacent each of two longitudinally extendingframe rails located beneath the body of the truck or trailer. Thesebeams are pivotally connected at one end to a hanger bracket extendingdownwardly from the frame, with an axle extending between the beamsadjacent the other end. Additionally, an air or coil spring is generallypositioned intermediate each frame rail and a corresponding beam. Thebeam may extend forwardly or rearwardly of the pivot, thus defining aleading or trailing beam suspension respectively.

Beam-type suspension systems are used on a significant number of trucksand trailers, and must have sufficient strength to resist lateral andaxial deflection while remaining stable. Lateral forces act on asuspension system in a variety of ways with the most common being thatlateral forces act on a suspension as a vehicle negotiates a turn. Asthe vehicle turns, shear stress acts between the tire and the roadsurface causing a lateral stress to be transferred through thetire-wheel assembly to the axle. The axle, being rigidly attached to thesuspension, transfers the lateral force into the beam causing it todeflect laterally. This lateral deflection can be extreme, and undercertain loading conditions, can cause the tires to contact the vehicleframe rails.

Roll stability refers to the counter-acting forces operating on the endsof an axle causing one end of the axle to raise relative to the frame adistance greater than the other end of the axle. Roll instability isencountered when the vehicle frame tilts or rolls relative to the axle;for example, when the vehicle negotiates a turn such that thecentrifugal and acceleration forces reduce the downward forces acting onthe inside wheel of the turn, and increase the downward force acting onthe outside wheel of the turn. Roll instability is also realized whenthe axle moves relative to the frame; for example, during diagonal axlewalk.

Diagonal axle walk occurs when the wheels of the opposite ends of theaxle encounter unlike irregularities in a road or off-the-road surface,such as when one wheel rides over a curb. As the wheel rides over thecurb, an upward force acts on that wheel, and a counteracting downwardforce acts on the wheel not riding over the curb. If the suspension isunable to provide flexibility between the axle and the frame as thetire-wheel assembly travels over the curb or ground irregularity, oralternatively to provide flexibility between the axle and the frame asthe vehicle negotiates a turn, the suspension will be roll rigid, andmay cause axle breakage or over stress vehicle components, such as theframe. As such, beam-type suspensions must be roll stable whileproviding sufficient vertical support to retain the vehicle above theroad surface.

Further, most vehicles designed with a beam-type suspension have a pathof travel which is parallel to the frame rails extending longitudinallyunder the vehicle. For vehicles having only a front and a rear axle, thevehicle path of travel is generally defined by the parallel and spacedapart rear tires such that the direction of travel of the rear tiresdefines the path of travel of the vehicle. For vehicles having only afront and a rear axle, this path of travel is adequate and safe even ifthe rear tires are not positioned parallel with the vehicle frame rails.However, when multiple axles are utilized, such as when auxiliarysuspension systems are provided on a vehicle, the path of travel of eachaxle must be aligned with the line of travel of the remaining axlescarried by the vehicle for safe vehicle operation.

Specifically, if one axle is aligned with the longitudinal frame railsextending under the vehicle, and a second axle is offset relative to thelongitudinal frame rails of the vehicle, as the vehicle moves over theroad surface, one axle and its associated tire-wheel assemblies willtrack along the path of travel of the vehicle, while the second axle,which includes tire-wheel assemblies which do not rotate in a directionparallel to the path of travel of the vehicle, will drag under thevehicle increasing tire scuffing, tire wear, and creating a generallyunsafe condition. When multiple axles are utilized, generally all tiresaffect the vehicle path of travel to some degree such that if one axleis offset relative to the vehicle path of travel, all tires will scuff,and drag under the vehicle. Additionally, as the tires drag under thevehicle due to their misalignment, they continually add lateral forcesto the suspension system, and consequently to the vehicle framesubstantially reducing the life span of both the vehicle frame andsuspension system components.

However, if the axles are aligned relative to the frame rails such thatthe tires rotate in a line parallel to the vehicle path of travel, thetire-wheel assemblies will rotate smoothly under the vehiclesubstantially increasing vehicle safety and vehicle performance as wellas substantially increasing tire life.

For the above reasons, and specifically for safety and vehicleperformance, it is necessary that each axle be carefully aligned withthe vehicle, and with other load bearing axles carried by the vehicle topresent a plurality of parallel and spaced apart tire-wheel assembliesfor engaging the road surface and defining the precise direction ofvehicle movement along the vehicles path of travel. Such alignment isdifficult for a number of reasons. Trailers as well as suspensionsystems may be manufactured out of tolerance, vehicle frame rails maynot be perfectly parallel, and suspension systems may not be accuratelymounted to the frame rails. These problems may be especially pronouncedwhen suspension systems are added to existing equipment which may haveexperienced significant use.

Thus, to accommodate for the above inconsistencies in manufacturing andsuspension system installation, an alignment mechanism is often includedas part of the suspension system such that after the suspension systemis installed on a vehicle, the axle may be moved relative to the vehicleto assure that the tire-wheel assemblies rotatably depending from theaxle are substantially parallel to the vehicle path of travel. While asignificant number of devices have been provided for this purpose, axlealignment continues to be a difficult process. Specifically, adjustingthe axle relative to the beams has a number of problems associatedtherewith. Alignment of the axle relative to the beam often includeswelding the adjustment collar to the mounting bracket after initialalignment. As such, it is difficult and expensive to realign the axleafter the vehicle has been in service.

An additional problem associated with trailing beam type suspensions isthe increased torque load which is input into the axle. Morespecifically, inasmuch as the beams are spaced apart a distance from 35inches to 41 inches, and each beam pivot point receives between 20,000and 30,000 pounds of force when engaging in roll or diagonal axle walk,with each beam length being approximately 20 inches, it is not uncommonfor the axle to be subjected to 50,000 foot pounds of torque in the areaintermediate the respective leading or trailing beams. The axle is thussubjected to extremely high torque loads substantially affecting theaxle and its operational characteristics. Additionally, the centralportion of the axle positioned intermediate the trailing beams is notreinforced, thereby further effecting the axle resistance to torqueload.

The need thus exists for a suspension system which is lightweight, isroll stable, and provides adequate vertical load-carryingcharacteristics, and which is resistant to lateral and longitudinalaxial forces. Additionally, the need exists for a suspension systemwhich provides an axle to beam connection which is lightweight, easy toassemble, simple to manufacture and easy to align relative to thevehicle path of travel. Still further, the need exists for a suspensionsystem which may be utilized as a tag axle, or alternatively as anauxiliary axle beneath a usual truck or trailer. The need also existsfor a suspension system which substantially eliminates axle torque whilestrengthening the central portion of the axle.

SUMMARY OF THE INVENTION

Objectives of the invention include providing a vehicle suspensionsystem which is roll stable, and resistant to lateral and longitudinalforces.

Another objective is to provide a suspension system which may beutilized as an auxiliary suspension or a principle suspension systemunder a usual truck or trailer.

Still another objective is to provide a vehicle suspension system whichmay be utilized as both a liftable and non-liftable suspension system.

A further objective is to provide a suspension system which utilizes asingle beam and a pair of control arms attached to the beam.

Yet another objective is to provide a suspension system whereby thesystem may be easily adjusted to assure that the path of travel of thetire-wheel assemblies attached to the axle are parallel with the vehiclepath of travel.

Yet a further objective is to provide a vehicle suspension system whichwill operate equally well on most vehicles.

Another objective is to provide a vehicle suspension system whichprovides a single beam attached to the axle along a relatively largeportion thereof.

Yet another objective is to provide a suspension system whereby thepivot axis of the central beam is aligned with the pivot axis of thecontrol arm.

Still a further objective of the invention is to provide a suspensionsystem which substantially eliminates axle torque while simultaneouslystrengthening the axle along its entire length.

Still a further objective of the invention is to provide a suspensionsystem having a single central beam, the characteristics of which may bevaried to provide either a roll flexible or a roll stiff suspensionsystem.

A still further objective is to provide such a vehicle suspension systemwhich is of simple construction, which achieves the stated objectives ina simple, effective and inexpensive manner, and which solves problemsand satisfies needs existing in the art.

These and other objectives and advantages of the invention are obtainedby the improved auxiliary suspension system, the general nature of whichmay be stated as including an axle; a suspension frame; a central beamhaving a pair of sides extending between the axle and suspension frame;a control arm extending between the central beam and the suspensionframe adjacent each side of the central beam; at least one air springadapted to be positioned intermediate the central beam and the vehicleframe; and at least one hanger bracket adapted for extending from thevehicle frame and for supporting the suspension system.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention, illustrative of the bestmode in which applicant has contemplated applying the principles, areset forth in the following description and are shown in the drawings andare particularly and distinctly pointed out and set forth in theappended claims.

FIG. 1 is a side elevational view of the suspension system of thepresent invention shown attached to a vehicle and with the tire-wheelassembly shown in dot-dash lines;

FIG. 2 is a rear end elevational view of the suspension system shown inFIG. 1;

FIG. 3 is an enlarged perspective view of the suspension system shown inFIG. 1 with the axle, tire-wheel, assemblies, and air springs removedwith portions broken away;

FIG. 4 is a perspective view of the center beam and control arms of thesuspension system shown in FIG. 3 with the axle removed and withportions cut away;

FIG. 5 is a sectional view taken along line 5--5, FIG. 3;

FIG. 6 is a perspective view of the beam shown in FIG. 4 with analternative bushing;

FIG. 7 is a perspective view of the beam and control arms of a secondembodiment of the present invention;

FIG. 8 is a perspective view of the beam and control arms of a thirdembodiment of the present invention;

FIG. 9 is a side elevational view with portions cut away and shown insection of the third embodiment of the present invention shown in afirst operating position;

FIG. 10 is a side elevational view with portions cut away and shown insection of the third embodiment of the present invention shown in asecond operating position; and

FIG. 11 is a side elevational view similar to FIG. 9 with an alternativelift mechanism.

Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The improved suspension system of the present invention is indicatedgenerally at 1 and is particularly shown in FIGS. 1 and 2 and isparticularly adapted to be mounted on a vehicle 2, such as a truck ortrailer. Vehicle 2 includes a cargo box 3 supported by a pair of sliderrails 4 extending longitudinally beneath vehicle 2. Suspension system 1includes a suspension frame 5 welded to a pair of parallel and spacedapart slide channels 6. Slide channels 6 are spaced apart a distanceequal to the distance between slider rails 4 and are mounted to sliderrails 4 with a plurality of mounting pins 7. Suspension system 1 furtherincludes a forward suspension 10 and a rearward suspension 11 forsupporting a forward axle 12 and a rearward axle 13, respectively. Eachaxle 12 and 13 supports a tire-wheel assembly 9 at each end thereof.Inasmuch as both the forward and rearward suspensions 10 and 11 aresimilar, only forward suspension 10 will be described in detail.

Referring to FIGS. 1-5, forward suspension 10 includes the suspensionsystem 1, a central beam 16 and a pair of parallel and spaced apartcontrol arms 17. Suspension frame 5 includes a front plate 20 and a rearplate 21, parallel to and spaced apart from front plate 20. A pair ofparallel and spaced apart hanger brackets 22 are positioned intermediatefront plate 20 and rear plate 21 adjacent the ends thereof. Each pair ofplates 22 are positioned apart a distance substantially equal to thewidth of slide channel 6 such that slide channel 6 may be welded theretoas shown specifically in FIG. 1. Additionally, each hanger bracket 22 isformed with an axially aligned hole 24 in the lower rear corner thereof.Two pair of parallel and spaced apart pivot flanges are positionedbetween front plate 20 and rear plate 21 and are formed with axiallyaligned holes 27, which holes 27 are also axially aligned with holes 24formed in hanger brackets 22. Front plate 20 and rear plate 21 areformed with a plurality of holes 28 to reduce the weight of suspensionsystem 1 and to provide access to the interior of suspension frame 5 forair and brake hoses.

In accordance with one of the main features of the present invention,and referring specifically to FIG. 4, central beam 16 includes a beamportion 30, and a pair of flanges having a top wall 31, a bottom wall 32and a pair of parallel and spaced apart sidewalls 33. Sidewalls 33include an inclined portion 34 and a substantially horizontal portion35. Beam portion 30 includes a forward end 38 and a rear end 39 withinclined portion 34 extending upwardly from horizontal portion 35 towardforward end 38.

Forward end 38 of top wall 31 and bottom wall 32 is formed with acentrally positioned U-shaped arcuate recess. A forward wall 36 extendsbetween sidewalls 3 and is substantially perpendicular thereto. Acylindrical outer housing 41 is also positioned intermediate top wall 31and bottom wall 32, adjacent sidewalls 33 and on either side of theU-shaped arcuate recess and houses an elastomeric bushing 42. Outerhousings 41 are spaced apart in the range of from 8 inches to 30 inches.Elastomeric bushing 42 is formed with an opening 43 whereby openings 43are axially aligned. Elastomeric bushings 42 may have a constant springrate in all directions, or alternatively may include a vertical springrate, a horizontal spring rate and an axial spring rate whereby each ofthe vertical spring rate, axial spring rate and horizontal spring ratediffer. The compliance of elastomeric bushing 45 may thus be tailored tothe particular needs of suspension system 1. More particularly, thespring rate of bushing 42 may be increased if a roll rigid suspension isrequired, or decreased if a roll flexible suspension is required.Additionally, the distance between outer housings 41 may be varied toprovide a more roll rigid or a more roll flexible suspension.Particularly, if tubular housings 41 and associated bushings 42 aremoved further apart, the suspension will be more roll rigid, and iftubular housings 42 are moved closer together, the suspension systemwill be more roll flexible. As such, the position of bushings 42 as wellas the spring rate of bushings 42 may be varied depending on theparticular requirements of suspension system 1.

Top wall 31 includes a forward plate 44 and a rear plate 45 secured tosidewalls 33. Rear plate 45 extends well over sidewalls 33 and issupported via a pair of vertical gussets 50 and 51 extending outwardlyfrom each sidewall 33. Gussets 50 and 51, and rear plate 45 combine toform a pivot flange 52 extending outwardly from each sidewall 33.Inasmuch as rear plate 45 extends over beam portion 30 of center beam 16and pivot flanges 52, pivot flanges 52 are extremely rigid and resistantto deflection. A U-shaped bracket 53 having a pair of legs 54 is mountedto the forward end of each pivot flange 52. A control arms 17 isreceived between legs 54 of each U-shaped bracket 53 and is securedtherebetween with a pivot pin 57. Control arms 17 may have a variety ofsizes and configurations, but in the preferred embodiment, they arecircular and include an adjustment mechanism for altering the length ofeach control arm 17. Still further, the adjustment mechanism isordinarily a turn-buckle arrangement whereby rotation of a central bar58 relative to the attachment ends 59 increases and decreases the lengthof each control arm 17. Still further, control arm 17 may be parallel,or be angled relative to one another without departing from the spiritof the present invention. Additionally, central beam portion 30 iscentrally positioned intermediate control arms 17 and is of sufficientwidth to offer roll stability to suspension system 1.

A bushing 60 extends around pivot pin 57 for providing compliancebetween control arms 17 and pivot pin 57. Similarly, each control arms17 has a free end 61 which houses a bushing 60 having a center aperture62 extending therethrough whereby central aperture 62 of bushings 60 areaxially aligned with central aperture 43 of bushings 42 housed withinouter housings 41 such that center beam 16 and control arm 56 pivotabout a common axis.

An axle cradle 65 is mounted to the rear end of central beam 16 andincludes a vertical support wall 66 having a flange 67 extendingoutwardly from each end thereof. Vertical wall 66 also includes aplurality of cut-outs 64. Each flange 67 is provided with a plurality ofoutwardly extending support gussets 68 having an arcuate top edge 69complementary shaped to receive axle 12. A center cradle 70 is providedwhich includes a bottom wall 71 and a pair of sidewalls 72 having a topedge 73 complementary shaped to receive axle 12. A weld plate 77 extendsdiagonally within center cradle 70 (FIG. 1), and operates to strengthencradle 70 and allow it to support axle 12. A weld plate 74 extendsupwardly from bottom wall 71 such that when axle 12 is positioned withinaxle cradle 65, it may be secured thereto via a weld at gussets 68,along top edge 69 at sidewalls 72, within cut-outs 64 and longitudinallyalong weld plate 74. In this manner, axle 12 is rigidly secured to axlecradle 65 and consequently to central beam 16. Additionally, this axleweld arrangement assures that axle 12 is welded to axle cradle 65 onlyalong the axle equator, that portion of the axle subject to the loweststrain.

Top wall 31, bottom wall 32, sidewalls 33, forward wall 36, and supportwalls 66 all combine to form box-shaped central beam 16 having aninterior cavity 75. A first strengthening rib 76 extends diagonallyacross central beam 16 within interior cavity 75 from the forward leftcorner to the rearward right corner while a second strengthening rib 76extends diagonally across central beam 16 from a right forward corner toa left rearward corner forming an X-shaped strengthening rib withininterior cavity 75. Strengthening rib 76 combine with top wall 31,bottom wall 32, sidewalls 33, gussets 50 and 51 to form an extremelyrigid central beam which deflects very little in response to lateral,longitudinal or roll forces inputted thereto from tire-wheel assemblies9.

Referring again to FIG. 3, each outer housing 41 of central beam 16extends intermediate one pair of pivot flanges 26 such that each opening43 of bushings 42 aligns with holes 27 formed in pivot flanges 26. Apivot bolt or pin then passes through holes 27 and opening 43 in eachbushing 42 to secure central beam 16 to suspension frame 5. Similarly,free end 61 of each control arms 17 is positioned between hangerbrackets 22 such that central aperture 62 is aligned with holes 24formed within hanger brackets 22 such that a pivot pin 81 passestherethrough to secure each control arms 17 intermediate hanger brackets22 and to suspension frame 5.

Referring next to FIGS. 1 and 2, three air spring mounting plates 82 aremounted on top of horizontal portion 35 of top wall 31. Similarly, threemounting plates 83 are mounted to the slider such that an air spring 84extends intermediate each mounting plate 82 and 83 for supporting thevertical load of vehicle 2. While three air springs are utilized in thepreferred embodiment, any number of air springs may be utilized withoutdeparting from the spirit of the present invention.

Operationally, suspension system 1 permits axle 12 to pivot about pivotpins 80 and 81 during use and in response to loads inputted intosuspension system 1 through tire-wheel assemblies 9. Specifically,suspension system 1 may be installed onto a usual vehicle 2 bypositioning hanger brackets 22 on either side of slide channels 6 andwelding the same thereto. Once suspension system 1 is secured to sliderails 6, axle 12 may be aligned by increasing or decreasing the lengthof one or both control arms 17. Specifically, central bar 58 may berotated to increase or decrease the length of the turn-buckle stylecontrol arms 17. By increasing and decreasing the length of a singlecontrol arm 17, one end of axle 12 will be moved forwardly or rearwardlyas adjustment requires. Central bar 58 may be rotated until tire-wheelassemblies 9 of axle 12 are aligned with the path of travel of theremaining tire-wheel assemblies of other axles attached to vehicle 2. Asthe length of control arms 17 is varied, bushings 42 will deflect withintubular outer housings 41 in order to assure that central beam 16 hassufficient compliance to move to a position substantially parallel tothe path of travel of vehicle 2.

Additionally, the spring rate of bushings 42 may be varied in order toincrease or decrease the roll compliance of the suspension system andtherefore offer a roll stable suspension to vehicle 2 as discussedabove. Still further, bushing 42 may be manufactured with varying springrates, and more particularly, bushings 42 may include a vertical springrate, and a horizontal spring rate different from the vertical springrate as well as an axial spring rate which differs from both thehorizontal spring rate and vertical spring rate thereby assuring thatsuspension system 1 may be tailored to meet the particular needs ofvehicle 2.

In accordance with one of the main features of the invention, centralbeam 16 offers roll resistance and lateral stability to suspensionsystem 1 via its welded interconnection with axle 12 and its bushedinterconnection with suspension frame 5. Conversely, control arms 17assists in reacting to longitudinal forces input into suspensionsystem 1. As can be seen from a review of FIGS. 1-5, suspension system 1substantially reduces the torque felt by axle 12 as central beam 16supports axle 12 along substantially the entire length thereof.Specifically, roll and lateral forces input into central beam 16 willreact at bushings 42, transfer into central beam 16, and out of centralbeam 16 through the other bushing 42. In this manner, a U-shaped rollbeam is provided whereby the path of travel of lateral and roll forcesinput into suspension system 1 does not include axle 12. As such, thetorque on axle 12 is substantially eliminated. Still further, inasmuchas central beam 16 attaches to axle 12 along a substantially largeportion of its length, axle 12 is reinforced.

When suspension system 1 engages in diagonal axle walk or receives rollforces as a result of vehicle 2 negotiating a turn, bushings 42 willprovide compliance in accordance with the design characteristics ofsuspension system 1. Suspension system 1 may be roll rigid or rollcompliant depending on the spring rate of bushings 42 as well as thedistance between bushings 42. As one end of axle 12 is raised, bushings42 will offer resistance, and transfer roll loads through central beam16 into the opposing bushing 42 and into the vehicle frame. As can beseen, inasmuch as beam 16 is attached to axle 12 adjacent its centralportion, and along a large portion of its length, very little torque isimparted into axle 12, but rather axle 12 is subjected only to bendingloads as a result of the movement of central beam 16 relative totire-wheel assemblies 9. This bending moment is strongly resisted viathe interconnection of axle 12 and central beam 16 through axle cradle65.

Similarly, when lateral force is applied to tire-wheel assemblies 28,for example, when vehicle 2 negotiates a turn, a forward edge of onebushing 42 and a rear edge of the other bushing will move intocompression thereby offering resistance to the movement of axle 12 as aresult of the horizontal spring rate of bushings 42. However, whenlongitudinal forces are inputted into tire-wheel assemblies 9, forexample, when the trailing beam suspension encounters an irregularity inthe road surface, or abuts an upstanding wall, such as a curb, controlarms 17 offers significant resistance against this movement as a resultof the rigid interconnection between suspension frame 5 and axle 12. Ascan be seen, suspension system 1 offers a roll stable suspension whichmay be either roll flexible or roll rigid depending on the verticalspring rate of bushing 42 and the distance between outer housings 41.Additionally, suspension system 1 is resistant to lateral force as aresult of the distance between bushings 42 and the fixed length ofcontrol arms 17 and to longitudinal forces as a result of control arms17. Additionally, as lateral force is input into suspension system 1,and force reacts at bushings 42, suspension system 1 will not translatelaterally, as control arms 17 are fixed in length and will not permiteither end of axle 12 to move outwardly from pivots 80 and 81.

Inasmuch as axle 12 is positioned within axle cradle 65, central beam16, control arms 17 and support frame 5 may be preassembled prior tointroduction of axle 12 substantially reducing manufacturing costs.

Referring next to FIG. 6, an alternative central beam is provided.Specifically, an alternative central beam indicated generally at 90 isshown in FIG. 6. Central beam 90 is identical to central beam 16 exceptthat it includes a single outer housing 91 housing a single bushing 92.Outer housing 91 is positioned between pivot flanges 26 in the mannerdescribed above such that a pivot pin 80 is positioned within bushing 92to secure central beam 90 to suspension frame 5. Operationally, if asingle bushing 92 is provided with an outer housing 91, variationbetween horizontal and vertical spring rates have less effect, andrather the conical spring rate of bushing 92 is critical and can bevaried to create either a roll rigid or roll compliant suspension systemdepending upon the requirements of vehicle 2.

A second embodiment of the central beam is shown in FIG. 7 and isindicated generally at 95. Alternative central beam 95 is identical tocentral beam 16 except it includes a pair of spaced apart sidewalls 96angled away from one another from forward end 38 to rear end 39. Asshould be apparent from a review of FIGS. 6 and 7, central beam 95 couldbe provided with a single outer housing as shown in FIG. 6 withoutdeparting from the spirit of the present invention. The forward end ofcentral beam 95 in the range of from 8 inches to 30 inches while therear end has a length in the range of from 10 inches to 60 inches, whilethe beam attaches to the axle in the range of from 35% to 90% of thetotal axle length.

Referring to FIGS. 8-10, a third embodiment of the invention is shownand is indicated generally at 100 with FIG. 8 depicting the central beamwhich is indicated generally at 101. Central beam 101 is identical tocentral beam 90 except that it includes a pair of spaced apart liftbrackets 102 secured to outer housing 91. Each lift bracket 102 isformed with a pair of outwardly extending legs 103 having a hole 104formed therein. A spring or lift weldment 105 is attached through holes104 via a bolt 106 so as to provide pivotal movement between each liftbracket 102 and spring weldment 105. Lift weldment 105 includes a springplate 107 and a pair of mounting flanges 108 extending downwardlytherefrom. A coil spring 109 is supported from spring plate 107 and iscompressed against a force plate 110 attached to suspension frame 5.Suspension system 100 operates identical to suspension system 1 exceptthat when air spring 84 is deflated, coil spring 109 will provide forceagainst lift bracket 102 welded to outer housing 91 opposite centralbeam 101 to apply a downward force thereto. As downward force is appliedto lift bracket 102, central beam 101 will pivot about pivot pin 80causing tire-wheel assembly 9 to move from the ground engaging positionshown in FIG. 9 to the non-ground engaging position shown in FIG. 10.Similarly, when air spring 84 is inflated, the force within air spring84 will cause central beam 101 to rotate downwardly from the positionshown in FIG. 10 to the position shown in FIG. 9 thereby applying anupward force to lift bracket 102 compressing coil spring 109.

Referring next to FIG. 11, a suspension system identical to suspensionsystem 100 is shown and includes an alternative lift mechanism 121.Specifically, air spring 122 is provided between spring weldment 105 andforce plate 110. Suspension system 120 operates identical to suspensionsystem 1 except that air spring 122 may be inflated and deflated inorder to move tire-wheel assembly 9 into and out of a ground engagingand a non-ground engaging position.

Accordingly, the invention described above, successfully overcomesproblems associated in the art, and creates a suspension system which isroll stable, resistant to lateral and longitudinal forces, and which maybe tailored to be roll flexible or roll rigid depending on theparticular requirements of vehicle 2. Moreover, the suspension systemwith the present invention provides an air ride suspension system whichis applicable as an auxiliary or primary suspension system, whetherliftable or non-liftable. The suspension system of the present inventionalso effectively eliminates the torque felt by the axle, and providesfor accurately aligning, and realigning the suspension system in asimple, and effective manner.

Accordingly, the improved center beam suspension system is simplified,provides an effective, safe, inexpensive, and efficient device whichachieves all the enumerated objectives, provides for eliminatingdifficulties encountered with prior devices, and solves problems andobtains new results in the art.

In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention is by way ofexample, and the scope of the invention is not limited to the exactdetails shown or described.

Having now described the features, discoveries and principles of theinvention, the manner in which the improved center beam suspensionsystem is constructed and used, the characteristics of the construction,and the advantageous, new and useful results obtained; the new anduseful structures, devices, elements, arrangements, parts andcombinations, are set forth in the appended claims.

I claim:
 1. A suspension system adapted to be mounted to a vehicle framecomprising:an axle; a suspension frame; a central beam having a pair ofsides extending between the axle and suspension frame; a control armextending between the central beam and the suspension frame adjacenteach side of the central beam; at least one air spring adapted to bepositioned intermediate the central beam and the vehicle frame; and atleast one hanger bracket adapted for extending from the vehicle frameand for supporting the suspension system.
 2. A suspension system adaptedto be mounted to a vehicle frame comprising:an axle; a suspension frame;a central beam non-rotatably secured to the axle and having a pair ofspaced apart sidewalls and one of a top wall and a bottom wall extendingbetween the axle and suspension frame; a rigid control arm extendingbetween the central beam and the suspension frame adjacent each side ofthe central beam; at least one air spring adapted to be positionedintermediate the central beam and the vehicle frame; at least one hangerbracket adapted for extending from the vehicle frame and for supportingthe suspension system; and a lifting mechanism for moving the axlebetween a lowered position and a raised position.
 3. The suspensionsystem as defined in claim 2 in which the lifting mechanism includes alift beam operationally connected to the axle whereby the lift beamincludes a spring plate, in which a force plate is attached to theframe, and in which a lift spring is interposed between the spring plateand the force plate for moving the axle between a raised position and alowered position.
 4. The suspension system as defined in claim 3 inwhich the lift spring is one of an air spring and a coil spring.
 5. Thesuspension system as defined in claim 3 in which a pivot means attachesthe force plate to the frame.
 6. The suspension system as defined inclaim 3 in which a pivot means attaches the spring plate to the liftbeam.
 7. The suspension system as defined in claim 2 further comprisinga central pivot for pivotally mounting the central beam to thesuspension frame, and in which the center beam extends away from thecentral pivot in one direction, and in which the lift beam extends awayfrom the central pivot in the opposite direction.
 8. The suspensionsystem as defined in claim 7 further comprising a central pivot forpivotally mounting the central beam to the suspension frame, and inwhich the lift mechanism is positioned forward of the central pivot.